System Administration Commands metadb(1M)
NAME
metadb - create and delete replicas of the metadevice state
databaseSYNOPSIS
/sbin/metadb -h
/sbin/metadb [-s setname]
/sbin/metadb [-s setname] -a [-f] [-k system-file] mddbnn
/sbin/metadb [-s setname] -a [-f] [-k system-file]
[-c number] [-l length] slice...
/sbin/metadb [-s setname] -d [-f] [-k system-file] mddbnn
/sbin/metadb [-s setname] -d [-f] [-k system-file] slice...
/sbin/metadb [-s setname] -i
/sbin/metadb [-s setname] -p [-k system-file]
[mddb.cf-file]
DESCRIPTION
The metadb command creates and deletes replicas of the meta-
device state database. State database replicas can be created on dedicated slices, or on slices that will later become part of a simple metadevice (concatenation or stripe) or RAID5 metadevice. Do not place state database replicas onfabric-attached storage, SANs, or other storage that is not
directly attached to the system and available at the same point in the boot process as traditional SCSI or IDE drives. See NOTES. The metadevice state database contains the configuration ofall metadevices and hot spare pools in the system. Addition-
ally, the metadevice state database keeps track of the current state of metadevices and hot spare pools, and their components. Solaris Volume Manager automatically updates the metadevice state database when a configuration or state change occurs. A submirror failure is an example of a statechange. Creating a new metadevice is an example of a confi-
guration change.SunOS 5.11 Last change: 29 Oct 2009 1
System Administration Commands metadb(1M)
The metadevice state database is actually a collection of multiple, replicated database copies. Each copy, referred to as a replica, is subject to strict consistency checking to ensure correctness. Replicated databases have an inherent problem in determining which database has valid and correct data. To solve this problem, Volume Manager uses a majority consensus algorithm. This algorithm requires that a majority of the database replicas be available before any of them are declared valid. This algorithm strongly encourages the presence of at least three initial replicas, which you create. A consensus canthen be reached as long as at least two of the three repli-
cas are available. If there is only one replica and the sys-
tem crashes, it is possible that all metadevice configura-
tion data can be lost. The majority consensus algorithm is conservative in the sense that it will fail if a majority consensus cannot be reached, even if one replica actually does contain the mostup-to-date data. This approach guarantees that stale data
will not be accidentally used, regardless of the failure scenario. The majority consensus algorithm accounts for the following: the system will stay running with exactly half or more replicas; the system will panic when less than half the replicas are available; the system will not reboot without one more than half the total replicas.When used with no options, the metadb command gives a short
form of the status of the metadevice state database. Usemetadb -i for an explanation of the flags field in the out-
put.The initial state database is created using the metadb com-
mand with both the -a and -f options, followed by the slice
where the replica is to reside. The -a option specifies that
a replica (in this case, the initial) state database shouldbe created. The -f option forces the creation to occur, even
though a state database does not exist. (The -a and -f
options should be used together only when no state databases exist.) Additional replicas beyond those initially created can be added to the system. They contain the same information as the existing replicas, and help to prevent the loss of the configuration information. Loss of the configuration makes operation of the metadevices impossible. To createSunOS 5.11 Last change: 29 Oct 2009 2
System Administration Commands metadb(1M)
additional replicas, use the metadb -a command, followed by
the name of the new slice(s) where the replicas will reside. All replicas that are located on the same slice must be created at the same time. To delete all replicas that are located on the same slice,the metadb -d command is used, followed by the slice name.
When used with the -i option, metadb displays the status of
the metadevice state databases. The status can change if a hardware failure occurs or when state databases have been added or deleted. To fix a replica in an error state, delete the replica and add it back again. The metadevice state database (mddb) also contains a list of the replica locations for this set (local or shared diskset).The local set mddb can also contain host and drive informa-
tion for each of the shared disksets of which this node is a member. Other than the diskset host and drive information stored in the local set mddb, the local and shared diskset mddbs are functionality identical. The mddbs are written to during the resync of a mirror orduring a component failure or configuration change. A confi-
guration change or failure can also occur on a single replica (removal of a mddb or a failed disk) and this causesthe other replicas to be updated with this failure informa-
tion. OPTIONS Root privileges are required for all of the followingoptions except -h and -i.
The following options can be used with the metadb command.
Not all the options are compatible on the same command line.Refer to the SYNOPSIS to see the supported use of the
options.-a
Attach a new database device. The /kernel/drv/md.confSunOS 5.11 Last change: 29 Oct 2009 3
System Administration Commands metadb(1M)
file is automatically updated with the new information and the /etc/lvm/mddb.cf file is updated as well. An alternate way to create replicas is by defining them in the /etc/lvm/md.tab file and specifying the assigned name at the command line in the form, mddbnn, where nnis a two-digit number given to the replica definitions.
Refer to the md.tab(4) man page for instructions on set-
ting up replicas in that file.-c number
Specifies the number of replicas to be placed on each device. The default number of replicas is 1.-d
Deletes all replicas that are located on the specified slice. The /kernel/drv/md.conf file is automatically updated with the new information and the /etc/lvm/mddb.cf file is updated as well.-f
The -f option is used to create the initial state data-
base. It is also used to force the deletion of replicasbelow the minimum of one. (The -a and -f options should
be used together only when no state databases exist.)-h
Displays a usage message.-i
Inquire about the status of the replicas. The output ofthe -i option includes characters in front of the device
name that represent the status of the state database. Explanations of the characters are displayed following the replica status and are as follows: d replica does not have an associated device ID. oSunOS 5.11 Last change: 29 Oct 2009 4
System Administration Commands metadb(1M)
replica active prior to last mddb configuration change u replica is up to date l locator for this replica was read successfully c replica's location was in /etc/lvm/mddb.cf p replica's location was patched in kernel m replica is master, this is replica selected as input r replica does not have device relocation information t tagged data is associated with the replica W replica has device write errors a replica is active, commits are occurring to this M replica had problem with master blocksSunOS 5.11 Last change: 29 Oct 2009 5
System Administration Commands metadb(1M)
D replica had problem with data blocks F replica had format problems S replica is too small to hold current database R replica had device read errors B tagged data associated with the replica is not valid-k system-file
Specifies the name of the kernel file where the replicainformation should be written. The default system-file
is /kernel/drv/md.conf. This option is for use with the local diskset only.-l length
Specifies the size of each replica. The default length is 8192 blocks, which should be appropriate for most configurations. "Replica" sizes of less than 128 blocks are not recommended.-p
Specifies updating the system file (md.conf) in the current working directory with entries from the /etc/lvm/mddb.cf file. This option is normally used to update a newly built system before it is booted for the first time. If the system has been built on a system other than the one where it will run, the location of the mddb.cf on the local machine can be passed as an argument. The system file to be updated can be changedSunOS 5.11 Last change: 29 Oct 2009 6
System Administration Commands metadb(1M)
using the -k option. This option is for use with the
local diskset only.-s setname
Specifies the name of the diskset on which the metadb
command will work. Using the -s option will cause the
command to perform its administrative function within the specified diskset. Without this option, the command will perform its function on local database replicas. sliceSpecifies the logical name of the physical slice (parti-
tion), such as /dev/dsk/c0t0d0s3.EXAMPLES
Example 1 Creating Initial State Database Replicas The following example creates the initial state database replicas on a new system.# metadb -a -f c0t0d0s7 c0t1d0s3 c1t0d0s7 c1t1d0s3
The -a and -f options force the creation of the initial
database and replicas. You could then create metadevices with these same slices, making efficient use of the system. Example 2 Adding Two Replicas on Two New Disks This example shows how to add two replicas on two new disks that have been connected to a system currently running Volume Manager.# metadb -a c0t2d0s3 c1t1d0s3
Example 3 Deleting Two ReplicasSunOS 5.11 Last change: 29 Oct 2009 7
System Administration Commands metadb(1M)
This example shows how to delete two replicas from the sys-
tem. Assume that replicas have been set up on /dev/dsk/c0t2d0s3 and /dev/dsk/c1t1d0s3.# metadb -d c0t2d0s3 c1t1d0s3
Although you can delete all replicas, you should never do so while metadevices still exist. Removing all replicas causes existing metadevices to become inoperable. FILES /etc/lvm/mddb.cf Contains the location of each copy of the metadevice state database. /etc/lvm/md.tab Workspace file for metadevice database configuration. /kernel/drv/md.confContains database replica information for all metadev-
ices on a system. Also contains Solaris Volume Manager configuration information. EXIT STATUS The following exit values are returned: 0 successful completion >0 an error occurredATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:SunOS 5.11 Last change: 29 Oct 2009 8
System Administration Commands metadb(1M)
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | storage/svm ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
SEE ALSO
mdmonitord(1M), metaclear(1M), metadetach(1M), metahs(1M), metainit(1M), metaoffline(1M), metaonline(1M), metaparam(1M), metarecover(1M), metarename(1M), metareplace(1M), metaroot(1M), metaset(1M), metassist(1M), metastat(1M), metasync(1M), metattach(1M), md.tab(4), md.cf(4), mddb.cf(4), md.tab(4), attributes(5), md(7D) NOTESReplicas cannot be stored on fabric-attached storage, SANs,
or other storage that is not directly attached to the sys-
tem. Replicas must be on storage that is available at the same point in the boot process as traditional SCSI or IDE drives. A replica can be stored on a: o Dedicated local disk partition o Local partition that will be part of a volume o Local partition that will be part of a UFS logging deviceSunOS 5.11 Last change: 29 Oct 2009 9